So this should work?
cat<<eof | gmt sample1d -Ap
5.53962564298 71.272033721
6.30984353357 71.4308039355
7.34727069584 71.4156247566
7.9243956509 71.1059801628
5.08609083753 71.2631386067
5.53962564298 71.272033721
eof
sample1d [ERROR]: x-values are not monotonically increasing/decreasing (at zero-based record 4)!
sample1d [ERROR]: Failure in gmt_intpol near row 5!